1. Field of Invention
The present disclosure relates generally to a nozzle for dispensing sealant on aircraft fasteners. More specifically, the present disclosure concerns nozzles adapted to enclose an exposed fastener head and meter an amount of sealant over the fastener head.
2. Description of Prior Art
Aircraft fuel tanks are typically assembled by fastening together sheets of metal or composite material. Fastening techniques include adhesive compounds, welding, and rivets. Riveting pierces the sheets being fastened thus creating a potential fluid leakage path along the rivet. To prevent leakage across the rivets, a sealant is generally applied along the interface between a fastener head and the exterior of the fuel tank. Referring now to FIG. 1A, a prior art example of a fastener 14 is shown attached to an upper fastened member 10. An interface 17 defines the fastener 14 to upper fastened member 10 contact periphery. Shown in sectional view in FIG. 1B, the fastener 14 includes a rounded head 16 set atop the upper fastened member 10. A shaft 18 depends from the head 16 through the upper fastened member 10 and into a lower fastened member 12. FIG. 1C illustrates in a side sectional view sealant 20 having been applied over the fastener head 16. The sealant 20 encompasses the interface 17 and extends past the interface 17 on the entire fastener 14 periphery.
FIGS. 2A through 2C illustrate a fastener 14A that includes a dome 19 projecting upward from an elliptically shaped base assembly 15. The base assembly 15 shown is mounted on the upper fastened member 10 with rivets 16A. As shown in side sectional view in FIG. 2B, the interface between the fastener 14A and upper fastened member 10 is defined by the outer periphery of the base assembly 15 adjacent the upper fastened member 10. Thus, sealant 20 (FIG. 2C) shown applied atop the fastener 14A extends along the outer periphery of the base assembly 15, thereby encompassing the interface 17A between the fastener 14A and upper fastened member 10.
Current techniques for applying sealant 20 to fasteners 14, 14A are typically manual such as brushing sealant onto the fastener or using a dispenser, with or without a metered supply of sealant 20. These current techniques can have results that vary with personnel applying the sealant and between applications performed by the same individual. These methods are also time consuming and often lead to an excess amount of sealant applied to the particular fastener 14, 14A. Since an aircraft can include a multiplicity of fasteners, the additive effect of excess sealant can unnecessarily increase overall aircraft weight.